The present invention relates to a method and apparatus for supplying tobacco or tobacco cutting machines. More particularly, the invention relates to improvements in a method and apparatus for supplying tobacco to one or more cutting machines which can be operated at a plurality of speeds, i.e., whose output is variable to insure that the rate of comminution is proportional to the rate of tobacco feed.
The commonly owned U.S. Pat. No. 3,801,024 to Elsner discloses an apparatus for comminuting tobacco wherein the tobacco compacting or condensing chains of the cutting machine (e.g., a shredding machine) receive tobacco from a container. Such machines can be used as a means for comminuting tobacco leaf laminae, tobacco ribs or reconstituted tobacco. As a rule, the moisture content of comminuted tobacco which issues from a cutting machine is much too high for immediate processing of such tobacco in a cigarette making or like machine. This is due to the fact that a modern high-speed cutting machine cannot properly comminute tobacco having a relatively low moisture content. Consequently, tobacco which is about to be comminuted must be moisturized and tobacco fragments (e.g., shreds) issuing from the cutting machine must be dried to reduce their moisture content. The drying of tobacco shreds must be carried out with a very high degree of accuracy because the moisture content of tobacco shreds in a modern cigarette maker must match a predetermined moisture content or can deviate from such predetermined moisture content by a small fraction of one percent. Therefore, a dryer which receives tobacco shreds from a cutting machine is a complex and expensive apparatus wherein the shreds remain for a relatively long interval of time in order to insure that the moisture content of each and every portion of the continuous tobacco stream issuing from the cutting machine equals or closely approximates the desired moisture content. The complexity of dryers for tobacco shreds is attributable primarily to two unpredictable parameters, namely the moisture content of shreds and the mass or quantity of tobacco issuing from the cutting machine. Fluctuations of the moisture content are due to a variety of reasons and, since the final moisture content is of utmost importance, the dryers are invariably designed to eliminate such fluctuations before the shreds are permitted to enter the distributor of a cigarette maker. Fluctuations in the quantity of tobacco issuing from the cutting machine (or from a battery of two or more parallel cutting machines) are also due to a host of factors, including the density of tobacco cake which is fed into the range of the moving knife or knives of a cutting machine, the temperature of tobacco to be comminuted, the moisture content of tobacco to be comminuted and the size of tobacco particles which are to be converted into a cake. It will be appreciated that the construction and operation of aforementioned dryers between the cutting machine or machines and a cigarette maker can be simplified and their output increased if the dryers must be designed exclusively for the purpose of reducing the moisture content, i.e., if such dryers receive tobacco shreds at a constant or nearly constant rate.
Heretofore known methods and apparatus for insuring that the dryers for tobacco shreds receive constant or substantially constant quantities of tobacco per unit of time have met with limited success, either because the apparatus are too complex and expensive or because they are incapable of insuring the delivery of constant quantities of tobacco so that the dryers which receive tobacco from such apparatus must be designed to compensate for fluctuations of moisture content as well as for fluctuations of the rate of tobacco delivery thereto. For example, U.S. Pat. No. 3,709,274 to Marek et al. discloses a method and apparatus for regulating output in tobacco cutting machines by measuring the density of tobacco flowing in the feed channel adjacent the cutting knives. The results of the measurements are used for regulation of tobacco input to the machine. Such mode of regulation causes a pronounced instability of the oncoming tobacco stream.
Commonly owned U.S. Pat. Nos. 3,736,942 and 3,807,415 to Elsber et al. disclose a weighing device downstream of a battery of tobacco cutting machines and a system which regulates the output of one of the machines so that the combined output remains constant. It has been found that such mode of operation causes pronounced instability in the rate of tobacco admission to as well as in the rate at which tobacco issues from the one machine. This will be readily appreciated by assuming that the weighing device indicates a reduction of the combined output at a time when the density of the tobacco cake entering the one machine is excessive. Consequently, the regulation immediately proceeds in the opposite direction.